1. Field of the Invention
This invention relates to the dyeing of natural proteinaceous and synthetic polyamide fibers, particularly nylons.
2. Description of the Prior Art
The dyeing of nylons--manufactured fibers in which the fiber-forming substance is any long chain synthetic polyamide having recurring amide groups as part of the chain--may, depending on the specific type of nylon involved--be accomplished with many different classes of dyestuffs e.g.: basic, acid, disperse, direct, etc. The acid dyes, which are in wide commercial use, are the class of dyestuffs utilized in this invention. For reasons of speeding of dyeing, maximum utilization of dyestuffs and improving evenness of color and trueness of hue throughout the dye fiber, dyestuffs are generally used in conjunction with "assistants" (sometimes designated as "carriers")--materials which promote the attainment of speedy dyeing, maximum dye utilization, etc.
Butyl benzoate and p-benzyl phenol are used commercially as dye assistants for nylons, however it was found in this work that p-benzyl phenol used as the sole effective component of a dye assistant for a particular specialty nylon, while giving high color intensity, gave poor evenness of color throughout the dye fiber. Unexpectedly, mixtures of p-benzyl phenol with butyl benzoate were found to be dye assistants which provide color intensity levels higher than those found with the individual compounds at the same level of concentration. And in addition, with the aforementioned specialty nylon, the mixture gave excellent evenness of color. Mixtures of lower alkyl esters of benzoic and toluic acid were disclosed in our U.S. Patent Applications Ser. Nos. 912,170 and 912,656 both filed June 5, 1978, as being effective, in combination with anyone of the materials listed below, as a dye assistant for acid and disperse dyes: alkyl esters of chlorinated benzoic acid, dibenzyl ether, dicyclopentenyl alcohol, methyl cellosolve benzoate, ethyl cellosolve benzoate and (3 hydroxy, 1-butoxy) tricyclo[5,2,1,0.sup.2,6 ]-4-decene. It has now been found that combination of butyl benzoate and this benzoic/toluic ester mixture can provide dye assistants which are more efficient than equal concentrations of the individual components of the mixture.